Weed Control and Selectivity to Post-Applied Herbicides in Eucalyptus

The objective of this study was to evaluate the selectivity of fluazifop-p-butyl and haloxyfop-R methyl ester on Eucalyptus urograndis (clone GG100), as well as the use of fluazifop-p-butyl for control of Panicum maximum and Urochloa brizantha. Two experiments were conducted in 15-liter capacity pots, in a completely randomized design with four replications. The first experiment consisted of seven treatments, in which fluazifop-p-butyl and haloxyfop-R methyl ester were sprayed at 15, 30 and 37 days after planting (DAP) and a control plot without application. In the second experiment, the treatments consisted of a factorial 4 × 2 (four application periods and two weed species), in which three seedlings of P. maximum or U. brizantha were transplanted per pot. In both experiments, at 90 DAP, plant height, stem diameter, leaf area and total dry matter of eucalyptus were evaluated. In the second experiment, besides the morphological parameters, the percentage of weed control was evaluated. The data was submitted to analysis of variance by F test, and the means compared by Tukey test at the level of 5% of probability. Both herbicides did not cause visual effects of phytointoxication in eucalyptus, but haloxyfop-R methyl ester was not selective to clone GG100 (E. urograndis). Fluazifop-p-butyl was selective to clone GG100, providing better control in the first application period (15 DAP) but only for P. maximum, which negatively affected the initial development of eucalyptus, while U. brizantha was not efficiently controlled with the usage of fluazifop-p-butyl.